On a cotton harvester having an onboard cotton module builder, also known as a cotton packager, the module or cotton package is formed by a compactor structure that moves in a vertical direction within a module builder or cotton compactor chamber, thereby pressing and compacting the cotton beneath the compactor structure against the chamber floor structure. Typically, augers on the compactor structure distribute the cotton within the compactor chamber and also act as compactor members for applying downward force against the cotton beneath the compactor structure when the compactor structure moves vertically down within the chamber. This results in a generally rectangular shape free-standing module of compacted cotton when subsequently unloaded onto the ground or another surface. Also typically, once unloaded, the top of the module is covered with a canvas or film tarp or cover. This is to prevent water from collecting on the module from rain or condensation prior to processing by a cotton gin. Cotton gins typically cannot process the cotton if the cotton is too high in moisture content. Recent advances in cotton compactor technology have provided the capability to densely pack the cotton, such that the module can substantially retain the shape of the module builder or compactor chamber, and such that the sides of the module will have a density that will shed water. However, it has been found that compactor structures having a flat shape will produce a module which is correspondingly flat on top. As a result, water can collect or pool on the module top, and there is a danger that even if covered, the water can seep or leak through the tarp or cover, to cause problems including a high moisture content, mold, or, if the moisture reaches the interior, heat buildup in the module.
Thus, what is sought is compactor structure for a cotton module builder capable of densely compacting the cotton, yet which overcomes one or more of the problems or shortcomings set forth above.